A Whangarei man who patrols local rivers to record pollution says he will go public with photos next week unless the Northland Regional Council takes action.
Millan Ruka, a member of the Environment River Patrol, says he has sent three reports in the past year of a large dairy herd grazing the banks of the Wairua River and fouling it.
He says the farmer has no water troughs in his paddocks and has ignored a council request to put up a fence.
Mr Ruka has told the council that unless it serves the farmer with an abatement notice by Monday, he will post his photos and identifying GPS data on a public internet site.
"I was hoping not to have to go that far. We want to be fair to farmers and the Northland Regional Council. It is time now - we've given several submissions in this regard to fencing out stock."
Millan Ruka says the farmer is flouting the Clean Streams Accord - the council's guidelines on riparian management - and the Resource Management Act requirement to avoid adverse effects on the environment.
The Northland Regional Council says it has no rules that can force farmers to fence off animals from rivers.